Secret knock project

Hi,

I am working on a secret knock project, I am using the piezo sensor linked below.

However, the sensor only detects the knocks if I directly tapped at it's white surface and when I just knock on the table where the piezo sensor is placed, it does not detect.

Also, when I placed a piece of wood with a thickness of 12 mm under the sensor, the sensor does not always detect the knock.

I appreciate the feedback.
Thanks.

FutureEngineer:
Hi,

I am working on a secret knock project, I am using the piezo sensor linked below.
Piezo Element - SEN-10293 - SparkFun Electronics

However, the sensor only detects the knocks if I directly tapped at it's white surface and when I just knock on the table where the piezo sensor is placed, it does not detect.

Also, when I placed a piece of wood with a thickness of 12 mm under the sensor, the sensor does not always detect the knock.

I appreciate the feedback.
Thanks.

Show us your code. (Between code tags please.)

Edit: I suspect that you have the threshold set too high.

I am testing the piezo sensor in simple sketch.

I am only displaying the values produced by the sensor at the serial monitor.

I do get appropriate reading when I tap at the white part of the sensor,

but if I knock at the table or at the piece of wood I placed on top of the sensor, the sensor detect the reading but not easily and not always

FutureEngineer:
I am testing the piezo sensor in simple sketch.

I am only displaying the values produced by the sensor at the serial monitor.

I do get appropriate reading when I tap at the white part of the sensor,

but if I knock at the table or at the piece of wood I placed on top of the sensor, the sensor detect the reading but not easily and not always

Well if you don't show your code to us, there's nothing we can do. And your schematic diagram.
Don't expect high values.

Edit: What do you consider an 'appropriate' value?